The present invention relates to a radiation image detector and a radiation image forming system which are used for X-ray mammography and for radiographing the chest and appendicular skeletons.
As s system used for radiographing an X-ray image for medical diagnosis, there has generally been used an image forming system wherein a silver halide photographic film is superposed closely on an X-ray intensifying screen and is exposed to an X-ray image to be developed, fixed, washed with water and dried by an automatic processor.
In the case of diagnoses by X-ray images for medical use and of non-destructive inspections, the so-called X-ray films employing a silver halide emulsion have widely been used. For diagnoses by images for medical use, in particular, a screen film system wherein an intensifying screen and an X-ray film are combined has been used for 100 years.
These image information are the so-called analog image information which make it impossible to conduct free image processing and instant electric transmission which can be conducted for digital image information which have recently been developed.
As one of digital technologies for X-ray images, computed radiography (CR) is currently accepted in the field of medical service. However, its sharpness is not enough, its spatial resolution is insufficient and it is unable to reach the level of image quality of the screen/film system. As a technology of digital X-ray image which is further new, there has been developed a flat panel X-ray detection device (FPD) employing a thin film transistor (TFT) which is described, for example, in John ROWLANDS"" thesis xe2x80x9cAmorphous Semiconductor Usher in Digital X-ray Imagingxe2x80x9d on page 24 of Nov. issue of the magazine xe2x80x9cPhysics Todayxe2x80x9d in 1997, or in L. E. ANTONUK""s thesis xe2x80x9cDevelopment of a High Resolution, Active Matrix, Flat-Panel Imager with Enhanced Fill Factorxe2x80x9d on page 2 of Volume 32 of the magazine xe2x80x9cSPIExe2x80x9d in 1997.
This has special features that a device is smaller and image quality is more excellent, compared with CR. However, on the other hand, it has a defect that resolution of images is as low as about 3-4 lp/mm, due to the restriction of a size of an image element owned by TFT. Further, as another X-ray digital technology, there is known a method to use an X-ray scintillator and a small number of CCDs. However, a radiation image detector employing a small number of CCDs has a weak point that it is large in size and heavy in weight.
The invention has been achieved in view of the actual circumstances stated above, and its first object is to provide a radiation image detector and a radiation image forming system wherein spatial resolution is high, image quality is high, and a thickness is small and weight is light. Further, the second object of the invention is to provide a radiation image pickup apparatus wherein it is possible to obtain an image which is free from optical distortion caused by positional deviation and/or change in size for an effective image area caused by change of ambient circumstances, mainly by change of temperature, and to process a large quantity of data rapidly.
To solve the problems stated above and to attain the objects, the invention is structured as follows.
(1-1) A radiation image detecting device, comprises: a scintillator to emit light in accordance with an intensity of radiation energy when being irradiated with radiation;
a lens array in which a plurality of lens units are arranged in a form of an array, wherein the light emitted from the scintillator passes through the lens array;
a lattice to partition the lens array, wherein the plurality of lens units are arranged on the lattice; and
a plurality of area sensors corresponding to the plurality of lens units of the lens array, the plurality of area sensors receiving the light having passed through the plurality of lens units and converting the light into electric signals,
wherein the scintillator, the lens array and the plurality of area sensors are arranged in that order.
(1-2) The radiation image detecting device of (1-1), wherein the lattice has a opaque member.
(1-3) The radiation image detecting device of (1-2), wherein a transmissivity of light having a wavelength of 400 nm to 700 nm for the lattice in not larger than 10%.
(1-4) The radiation image detecting device of (1-1), wherein the scintillator emits visible light in accordance with an intensity of radiation energy.
(1-5) The radiation image detecting device of (1-4), wherein the scintillator contains gadolium oxysulfide (Gd2O2S:Tb) or cesium iodide (CsI:Tl).
(1-6) The radiation image detecting device of (1-1), wherein each lens unit in the lens array comprises plural different lenses.
(1-7) The radiation image detecting device of (1-6), wherein a magnification of the each lens unit is 1/1.5 to 1/20.
(1-8) The radiation image detecting device of (1-6), wherein an effective F-number of the each lens unit is not larger than 8.
(1-9) The radiation image detecting device of (1-6), wherein a difference of MTF between a center and a periphery on an forming plane by the each lens unit is not larger than 30%.
(1-10) The radiation image detecting device of (1-6), wherein a half field angle of the each lens unit is not more than 35xc2x0.
(1-11) The radiation image detecting device of (1-6), wherein the each lens unit comprises a focus point adjusting device.
(1-12) The radiation image detecting device of (1-6), wherein the each lens unit contains Pb by 0.47 wt % or more and less than 69 wt % of a total weight of glass components of the each lens unit.
(1-13) The radiation image detecting device of (1-6), wherein the each lens unit contains PbO by 0.5 wt % or more and less than 75 wt % of a total weight of glass components of the each lens unit.
(1-14) The radiation image detecting device of (1-1), wherein the area sensors comprises a solid-state image acquiring unit such as a CCD or a CMOS sensor.
(1-15) The radiation image detecting device of (1-1), further comprising a transparent member provided between the scintillator and the lens array.
(1-16) The radiation image detecting device of (1-15), wherein the transparent member comprises a glass and the transparent member contains Pb by 0.47 wt % or more and less than 69 wt % of a total weight of glass components of the transparent member.
(1-17) A radiation image detecting device, comprises:
a scintillator to emit light in accordance with an intensity of radiation energy when being irradiated with radiation;
a lens array comprising a plurality of lens unit, wherein the light emitted from the scintillator passes through the lens array; and
a plurality of area sensors corresponding to the plurality of lens unit of the lens array, the plurality of area sensors receiving the light having passed through the plurality of lens units and converting the light into electric signals,
wherein the scintillator, the lens array and the area sensors are arranged in this order and a focus length f (mm) of each lens unit satisfies the following formula:
2 less than f less than 20.
(1-18) A radiation image detecting apparatus, comprises:
a scintillator to emit light in accordance with an intensity of radiation energy when being irradiated with radiation;
a transparent member, wherein the light emitted from the scintillator passes through the transparent member;
a lens array comprising a plurality of lens units, wherein the light having passed through the transparent member further passes through the lens array; and
a plurality of area sensors corresponding to the plurality of lens units of the lens array, the plurality of area sensors receiving the light having passed through the lens arrays and converting the light into electric signals,
wherein the scintillator, the transparent member, the lens array and the plurality of area sensors are arranged in that order.
Here, it may be preferable that the apparatus described in (1-17) or (1-18) is used in combination with at least one of the structures of (1-1) to (1-16).
(1-19) A radiation image detecting apparatus, comprises:
a scintillator to emit light in accordance with an intensity of radiation energy when being irradiated with radiation;
a lens array comprising a plurality of lens units, wherein the light emitted from the scintillator passes through the lens array;
a plurality of area sensors corresponding to the plurality of lens units of the lens array, the plurality of area sensors receiving the light having passed through the lens arrays and converting the light into electric signals, and each area sensor having an effective imaging region, and
correcting means for correcting the electric signals so as to correct at least one of a change in a position of the effective imaging region of each area sensor and a change in a size of the effective imaging region of each area sensor;
wherein the scintillator, the lens array and the plurality of area sensors are arranged in that order.
Also, it may be preferable that the apparatus described in (1-19) is used in combination with at least one of the structures of (1-1) to (1-18).
(1-20) The radiation image detecting apparatus of (1-19), further comprises:
a memory to store information regarding the position of the effective imaging region of each area sensor, and
wherein the correcting means corrects the change in the position of the effective imaging region of each area sensor based on the information regarding the position of the effective imaging region.
(1-21) The radiation image detecting apparatus of (1-19), further comprises:
a memory to store information regarding the size of the effective imaging region of each area sensor,
wherein the correcting means corrects the size of each area sensor based on the information regarding the size.
(1-22) The radiation image detecting apparatus of (1-19),
wherein the correcting means corrects a change in the size of the effective imaging region of each area sensor based on the information regarding the size.
(1-23) A radiation image detecting apparatus, comprises:
a scintillator to emit light in accordance with an intensity of radiation energy when being irradiated with radiation;
a lens array comprising a plurality of lenses, wherein the light emitted from the scintillator passes through the lens array;
a plurality of area sensors corresponding to the plurality of lenses of the lens array, the plurality of area sensors receiving the light having passed through the lens array and converting the light into electric signals; and
correcting means for correcting the electric signals so as to correct an optical deformation caused by each lens based on data acquired by radiographing a lattice-shaped object;
wherein the scintillator, the lens array and the plurality of area sensors are arranged in that order.
Further, the above object may be attained by the following preferable structures.
(2-1) A radiation image detector which is composed of an X-ray scintillator, a lens array and an area sensor which corresponds to each lens unit of the lens array all arranged in this order.
Since an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array are arranged in this order in the invention described in Item (2-1), spatial resolution is high, image quality is high, a thickness is small, a size is small and weight is light.
(2-2) The radiation image detector described in Item (2-1) wherein the X-ray scintillator of gadolium oxysulfide (Gd2O2S:Tb) or cesium iodide (CsI:Tl) generates visible light when it is exposed to X-rays.
Since the X-ray scintillator of gadolium oxysulfide (Gd2O2S:Tb) or cesium iodide (CsI:Tl) generates visible light when it is exposed to X-rays in the invention described in Item (2-2), spatial resolution is high and image quality is high.
(2-3) The radiation image detector described in Item (2-1) wherein the lens array is composed of a lens unit made of combination of plural different lenses in quantity of two or more.
Owing to the invention described in Item (2-3) wherein the lens array is composed of a lens unit made of combination of plural different lenses in quantity of two or more, spatial resolution is high, image quality is high, and a thickness can be made small.
(2-4) The radiation image detector described in Item (2-3) wherein magnification of the lens unit is in a range from 1/1.5 to 1/20.
In the case of the invention described in Item (2-4), magnification of the lens unit is in a range from 1/1.5 to 1/20, and when it is greater than 1/1.5, an area sensor is too big to make arrangement difficult, while when it is smaller than 1/20, a distance from the X-ray scintillator to the lens unit is long to increase a thickness of the radiation image detector.
(2-5) The radiation image detector described in Item (2-3) or Item (2-4) wherein the effective F number of the lens unit is not more than 8.
Owing to the invention described in Item (2-5) wherein the effective F number of the lens unit is not more than 8, it is possible to realize a highly sensitive detector by enhancing the light-converging efficiency.
(2-6) The radiation image detector described in either one of Items (2-3)-(2-5) wherein a difference of MTF between the center and a periphery on the image plane of the lens unit is within 30%.
Owing to the invention described in Item (2-6) wherein a difference of MTF between the center and a periphery on the image forming plane of the lens unit is within 30%, it is possible to obtain sharp and clear images. Here, xe2x80x9cMTFxe2x80x9d is a abbreviation of Modulation Transfer Function, a ratio of a visibility on an object surface and a visibility on an image surface when a sine curve chart is photographed, and represents a image forming performance of a lens. As to further detailed information about xe2x80x9cMTFxe2x80x9d, the description on page 151 on the publication of Optical Technical Hand Book published by Asakura Shoten may be referred.
(2-7) The radiation image detector described in either one of Items (2-3)-(2-6) wherein a half field angle of the lens unit is not more than 35xc2x0.
Owing to the invention described in Item (2-7), wherein a half field angle of the lens unit is not more than 35xc2x0, it is possible to make a fall of a quantity of light on the periphery of an image formed by the lens unit to be less, and to raise sensitivity of a radiation image detector.
(2-8) The radiation image detector described in either one of Items (2-3)-(2-7) wherein each lens unit stated above has its own focusing means.
Owing to the invention described in Item (2-8), wherein each lens unit has its own focusing means, it is possible to obtain sharp and clear images by focusing each lens unit of the lens array by use of a spacer, correcting errors in manufacture of the lens unit and by distortion of a detector itself.
(2-9) The radiation image detector described in either one of Items (2-3)-(2-8) wherein a lens array is partitioned by a lattice and the lens unit is arranged in the lattice.
Owing to the invention described in Item (2-9) wherein a lens array is partitioned by a lattice, it is possible to enhance physical strength of a detector and to maintain sharp images for a long time. By using opaque plastics or metal as a material of the lattice, it is possible to prevent light-spreading from a lens to a lens, and to obtain sharp images.
(2-10) The radiation image detector described in either one of Items (2-3)-(2-9) wherein the lens unit contains PbO in the amount of 0.5% or more and less than 75% by weight of the total glass components of the lens unit.
Owing to the invention described in Item (2-10) wherein the lens unit contains lead oxide in the amount of 0.5% or more and less than 75%, it is possible to prevent deterioration of an area sensor caused by X-ray irradiation.
(2-11) The radiation image detector described in Item (2-1) wherein the area sensor is made up of a solid image pickup element such as CCD or CMOS sensor.
Owing to the invention described in Item (2-11) wherein a solid image pickup element such as CCD or CMOS sensor is used as the area sensor, it is possible to obtain sharp and clear images.
(2-12) The radiation image detector described in Item (2-1) wherein a transparent member is provided between the X-ray scintillator and the lens array.
Owing to the invention described in Item (2-12) wherein a transparent member is provided between the X-ray scintillator and the lens array, it is possible to prevent scratches on the X-ray scintillator caused by the lattice.
(2-13) The radiation image detector described in Item (2-1) wherein a transparent glass plate containing PbO in the amount of 0.5% or more and less than 75% is provided between the X-ray scintillator and the area sensor.
Owing to the invention described in Item (2-13) wherein the glass plate contains lead oxide in the amount of 0.5% or more and less than 75%, it is possible to prevent deterioration of the area sensor caused by X-ray irradiation.
(2-14) A radiation image forming system wherein radiation images are detected by the radiation image detector described in either one of Items (2-1)-(2-13), X-ray images are taken out of the radiation image detector as image signals, the image signals are transformed into laser beam intensity fluctuation, a silver halide photographic light-sensitive material having at least one light-sensitive silver halide emulsion layer is subjected to scanning exposure, then, development is made by using alkaline processing composition containing therein silver halide solvent to make at least a part of unexposed silver halide in the aforesaid light-sensitive silver halide emulsion layer to be diffusible silver complex, at least a part of the diffusible silver complex is transferred onto a silver depositing nucleus-containing image receiving layer to form images on the silver depositing nucleus-containing image receiving layer, and the silver depositing nucleus-containing image receiving layer is separated from a light-sensitive element after the image forming to obtain X-ray images.
X-ray images having high sharpness, high resolution and high image quality which are required, for example, for mammography and appendicular skeleton can be obtained rapidly and surely by the invention described in Item (2-14) wherein X-ray images are taken out of the radiation image detector as image signals, the image signals are transformed into laser beam intensity fluctuation, a silver halide photographic light-sensitive material having at least one light-sensitive silver halide emulsion layer is subjected to scanning exposure, then, development is made by using alkaline processing composition containing therein silver halide solvent to make at least a part of unexposed silver halide in the aforesaid light-sensitive silver halide emulsion layer to be diffusible silver complex, at least a part of the diffusible silver complex is transferred onto a silver depositing nucleus-containing image receiving layer to form images on the silver depositing nucleus-containing image receiving layer, and the silver depositing nucleus-containing image receiving layer is separated from a light-sensitive element after the image forming to obtain X-ray images.
(2-15) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and an effective image area rate of the area sensor is within a range from 5% to 99%.
The invention described in Item (2-15) wherein an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array are arranged in this order, makes spatial resolution and image quality to be high, and makes the apparatus to be thin in thickness, small in size and light in weight.
Further, by making an effective image area rate of each area sensor to be 99% or less, it is possible to obtain images of high resolution, even when positional deviation and/or change in size of an effective image area is caused by changes in ambient circumstances, mainly by changes in temperature. Further, by making the effective image area rate to be 5% or more, it is possible to utilize an area sensor effectively, and to prevent a fall of resolution (reduction of the number of pixels in an area sensor for a divided image area).
(2-16) The radiation image pickup apparatus described in Item (2-15) wherein the effective image area rate of each area sensor is within a range from 50% to 90%.
Owing to the invention described in Item (2-16), when the effective image area rate of each area sensor is made to be 90% or less, it is possible to obtain images of high resolution even when positional change of an effective image area and/or change in size of an effective image area is caused more severely by changes in ambient circumstances, mainly by changes in temperature. Further, by making the effective image area rate of each area sensor to be 50% or more, it is possible to utilize an area sensor more effectively, and to prevent a fall of resolution (reduction of the number of pixels in an area sensor for a divided image area).
(2-17) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and an image data preparing means which prepares total image data from image signals of an effective image area of each area sensor stated above is provided.
Owing to the invention described in (2-17), it is possible to obtain image data rapidly by preparing total image data by the use of only signals of an effective image area out of image signals of all image areas of each area sensor.
(2-18) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and an image data preparing means which prepares total image data from image signals of an area broader than the effective image area of each area sensor stated above is provided.
In the invention described in Item (2-18), by preparing the total image data by the use of signals of the area which is broader than the effective image area among total image areas on each area sensor, for example, the total image area or the area obtained by eliminating outermost several lines from the total image area, it is possible to average data and to obtain image data having less noise.
(2-19) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and a correction means which corrects positional change of an effective image area and/or change in size for an effective image area of each area sensor is provided.
By correcting positional change of an effective image area and/or change in size of an effective image area for the initial position in photographing in the invention described in Item (2-19), it is possible to obtain images of high resolution even when positional change of an effective image area and/or change in size of an image of the effective image area formed on an area sensor is caused by ambient circumstances, mainly by temperature.
(2-20) The radiation image pickup apparatus described in Item (2-19) wherein the radiation image detector has a correction data storage means which stores correction data prepared in advance for positional change of an effective image area and/or change in size for an effective image area, and positional change of an effective image area and/or change in size for the effective image area of each area sensor is corrected by the use of the correction data for positional change of an effective image area and/or change in size for the effective image area.
In the invention described in Item (2-20), by preparing in advance the correction data for positional change of an effective image area and/or change in size for an effective image area for correcting positional change of an effective image area and/or change in size for the effective image area, it is possible to obtain images of high resolution even when positional change of an effective image area and/or change in size of an image of the effective image area formed on an area sensor is caused by ambient circumstances, mainly by temperature.
(2-21) The radiation image pickup apparatus described in Item (2-20) wherein correction data for positional change of an effective image area and/or change in size for the effective image area are those obtained through photographing of a lattice-shaped object.
In the invention described in Item (2-21), by preparing correction data in a method wherein a lattice-shaped object is photographed for preparation of correction data, and image data obtained from the photographing are made to correspond to the image of the lattice-shaped object photographed originally, it is possible to obtain images of high resolution even when positional change of an effective image area and/or change in size of an image of the effective image area formed on an area sensor is caused by ambient circumstances, mainly by temperature.
(2-22) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and a correction means which corrects optical distortion caused by the lens unit is provided.
Owing to the invention described in Item (2-22), it is possible to obtain images of high resolution by correcting optical distortion caused by the lens unit, even when distortion of an image formed on an area sensor is caused.
(2-23) The radiation image pickup apparatus described in Item (2-22) wherein the radiation image detector has a correction data storage means which stores correction data prepared in advance for distortion, and optical distortion caused by the lens unit is corrected by the use of the correction data for distortion.
By preparing correction data in advance for correcting optical distortion and by correcting optical distortion by the use of correction data for image data obtained through photographing in the invention described in Item (2-23), it is possible to obtain images of high resolution even when distortion of an image formed on an area sensor is caused.
(2-24) The radiation image pickup apparatus described in Item (2-23) wherein the correction data for distortion are those obtained through photographing of a lattice-shaped object.
In the invention described in Item (2-24), by preparing correction data in a method wherein a lattice-shaped object is photographed for preparation of correction data, and image data obtained from the photographing are made to correspond to the image of the lattice-shaped object photographed originally, it is possible to obtain images of high resolution even when distortion of an image formed on an area sensor is caused by ambient circumstances, mainly by temperature.
(2-25) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and there are provided an irradiation field recognition means which conducts irradiation field recognition from all image data obtained by the radiation image detector and an image processing means which eliminates or compresses data outside the irradiation field.
By eliminating or compressing image data of pixels outside an irradiation field which are not necessary for diagnoses and by making an amount of total image data small in the invention described in Item (2-25), it is possible to process a large quantity of data quickly.
(2-26) A radiation image pickup apparatus wherein a radiation image detector composed of an X-ray scintillator, a lens array and an area sensor corresponding to each lens unit of the lens array all arranged in this order is provided, and there are provided a ROI recognition means which conducts ROI recognition from all image data obtained by the radiation image detector and an image processing means which eliminates or compresses data outside ROI.
By eliminating or compressing image data of pixels outside ROI which are not necessary for diagnoses and by making an amount of total image data small in the invention described in Item (2-26), it is possible to process a large quantity of data quickly.
(2-27) The radiation image pickup apparatus described in Item (2-25) or (2-26) wherein the radiation image detector prepares total image data from image signals of each area sensor, after positional change of an effective image area and/or change in size for an effective image area is corrected in each area sensor.
By superposing image data from image signals of each area sensor and by preparing total image data after positional change of an effective image area and/or change in size for an effective image area is corrected in each area sensor. in the invention described in Item (2-27), it is possible to obtain images of high resolution even when positional change of an effective image area and/or change in size of an image of the effective image area formed on an area sensor is caused by ambient circumstances, mainly by temperature.
(2-28) The radiation image pickup apparatus described in Item (2-25) or (2-26) wherein the radiation image detector prepares total image data from image signals of each area sensor, after distortion is corrected in each area sensor.
Owing to the invention described in Item (2-28), it is possible to obtain images of high resolution by superposing image data from image signals of each area sensor and by preparing total image data after distortion is corrected in each area sensor, even when distortion of an image formed on an area sensor is caused.
(2-29) The radiation image pickup apparatus described in Item (2-25) or (2-26) wherein the radiation image detector conducts irradiation field recognition processing after total image data from image signals of each area sensor is prepared.
In the invention described in Item (2-29) wherein irradiation field recognition processing is conducted after total image data from image signals of each area sensor are prepared, it is possible to process a large quantity of data rapidly by eliminating or compressing image data of pixels outside an irradiation field which are not necessary for diagnoses to make an amount of total image data small.
(2-30) The radiation image pickup apparatus described in Item (2-25) or (2-26) wherein the radiation image detector conducts ROI recognition processing after total image data from image signals of each area sensor are prepared.
In the invention described in Item (2-30) wherein ROI recognition processing is conducted after total image data from image signals of each area sensor are prepared, it is possible to process a large quantity of data rapidly by eliminating or compressing image data of pixels outside ROI which are not necessary for diagnoses to make an amount of total image data small.
(2-31) The radiation image pickup apparatus described in Item (2-25) or (2-26) wherein the radiation image detector conducts gradation processing, frequency processing and equalization processing, after irradiation field recognition processing and/or ROI recognition processing is conducted.
In the invention described in Item (2-31), it is possible to process a large quantity of data rapidly by conducting gradation processing, frequency processing and equalization processing, after irradiation field recognition processing and/or ROI recognition processing is conducted.
(2-32) The radiation image pickup apparatus described in Item (2-25) or (2-26) wherein the radiation image detector conducts ROI recognition processing after irradiation field recognition processing.
In the invention described in Item (2-32), it is possible to process a large quantity of data rapidly by conducting ROI recognition processing after conducting irradiation field recognition processing.